The view of a 16th-century Lisbon street is such a teeming hodgepodge of races, social classes and religions and has so much life on display — much of it mischievous — that's it hard not to smile.

Slightly to the right of center, an African man wearing the wide pants of a sailor dances with a stranger. He's trying to embrace a middle-aged white woman carrying a jug, who recoils in surprise.

Toward the left, two Jewish policemen — identifiable by their long beards and armbands — support a sheepish-looking black prisoner who appears to be drunk.

At the lower right, a black man on horseback bears the scarlet insignia of the Order of St. James on his cloak and is clearly a nobleman. And from the window of a nearby tower, an elegantly dressed white woman gazes down on the scene, clearly as fascinated by the goings-on as we are.

Within its rough-hewn frame, "Public Square with the King's Fountain," which is thought to have been painted about 1580 by an unknown Flemish artist, has something both joyous and vital to say about the lives of black people in Renaissance Europe — the theme of new exhibit opening today at the Walters Art Museum.

The exhibit, which contains 73 paintings, sculptures, prints and manuscripts by such artists as Peter Paul Rubens, Domenico Tintoretto and Albrecht Durer, was a 10-year undertaking for Joaneath Spicer, the Walters' curator of Renaissance and Baroque art. After the show closes in January, it will travel to the Princeton University Art Museum, which co-sponsored the exhibit.

The show also is an important piece of scholarship, because it is the first time that a major art museum has taken a systematic look at Europe's black inhabitants in the 15th through 17th centuries.

(In 2008, Amsterdam's De Nieuwe Kerk held a show called "Black Is Beautiful" that looked at representations of Africans in Dutch art from the Middle Ages to the present. But that exhibit was less historically focused and lighter in tone than the Walters' show.)

"It's an act of courage for a museum to tackle this topic," museum director Gary Vikan says. "Even though Europe in 1550 is not the United States in 2012, an exhibit like this still brings us right back home to where we are now as a society in terms of tackling issues of race."

Spicer says that she's wanted to do a show like this one since 1990, when she was contacted by a Boston researcher studying a 16th-century painting by Jacopo da Pontormo of two members of the notorious de' Medici family, a woman and her little ward, Giulia.

Was it possible, the researcher wanted to know, that Giulia was of African ancestry?

Spicer was intrigued, because Giulia was the illegitimate daughter of the tyrant Alessandro de' Medici, the Duke of Florence — and himself widely thought to be the son of a Roman Catholic cardinal and a black woman.

The curator concluded that Pontormo's 1539 painting is the first depiction of a girl of African ancestry in European art.

Even more intriguingly, when the painting was acquired by the museum's founder, Henry Walters, in 1902, no child was visible.

Giulia had literally been "blacked out" by an unscrupulous dealer some time between 1814 and 1881. It wasn't until 1937, when the portrait was being readied for cleaning, that an X-ray revealed Giulia's ghostlike image hiding beneath the top coat of paint. Later, the extra layer was removed, and the little girl was restored to her rightful position between her guardian's protective hands.

Within the exhibit, Africans and those of African descent are depicted as Magi, warriors, merchants, royalty, jesters, doctors, saints.

Though the first European slaves were mostly white prisoners from Russia or central Asia (hence the similarity to the word "Slavic") the exhibit doesn't shy away from the casual contempt in which subjugated peoples were treated by their masters.

So for instance, the exhibit contains a selection of oil lamps from the 1500s that were shaped like the heads of African servants. The subjects' mouths are agape, and the wick all-too-aptly takes the place of their tongues.

The exhibit also locates the roots of prejudice based on skin color in a distinction between day and night that Spicer says is present throughout religions.

Daylight was associated with illumination and truth, according to an exhibition wall text, and nighttime darkness with sin and evil. It didn't take long for ancient peoples to extend the metaphor and begin making moral judgments based on skin tones that vary between pale beige and chocolate brown.

Museum officials were aware that speculating about the origins of racial prejudice may offend some visitors. While the exhibit was in the planning stages, they met with community representatives, including a Walters trustee who participated in civil rights demonstrations in the 1960s.

As Vikan put it: "Every interested party or even potentially interested party has been part of the conversation."

Spicer said that a colleague at the Walters reported feeling furious and upset after reading the wall text that revealed that the supposed "curse of Ham" — which asserts that the dark skin of African people is a mark of sin — came from forged documents that were passed off as ancient writings.

"If it makes you mad," Spicer says, "if it makes you livid, that's the point."

Ben Vinson, a professor at Johns Hopkins University's Center for Africana Studies, is one of several community leaders who became involved in the exhibit in 2008 as a consultant on issues of historical accuracy. He thinks that the Walters has handled potentially explosive material sensitively.

"People have seen these images individually in books, but they've never been able to walk through a museum and see them and experience them together, and for that I commend the Walters," he says.

"It's the role of a museum to put hard issues out there so we can think about them. And, when we're talking about race, nothing is hallowed ground. We need to be honest in our conversation and put our cards on the table if we're ever able to achieve reconciliation. I believe that this exhibit will further the debate about race in our community."

For artists, beauty has never been skin-deep. For instance, Spicer says, Renaissance sculptors who worked with such naturally copper-colored materials as bronze or iron often chose African subjects for their statuettes. These artworks celebrate the proportions and burnished complexions of their human models.

And, it's equally clear that the painters were as likely as the sculptors to perceive their African neighbors not as stereotypes, but as individuals.

One of the many treasures of the exhibition is Rubens' 1609 oil sketch of a turbaned North African diplomat. The sketch was prepared for the artist's own use and seems to have been dabbed on whatever paper was at hand. (In this case, the rows of vertical writing seem to indicate that Rubens painted over a text of some kind.)

Viewers' eyes rest first on the white turban swaddling the man's face. Then, we notice the teeth exposed in the partially open mouth and the gleam in his right eye. The implication is unmistakable: the artist has caught this canny politician in mid-calculation.

A portrait of a very different sort is on display in an earlier gallery, Durer's study of a 20-year-old slave named Katharina.

Spicer says that if museum visitors look at just one painting in the exhibit, it should be this portrait, which is being exhibited for the first — and perhaps the only — time in the western hemisphere. (This sketch will not travel to Princeton with the rest of the exhibit, but will return to Florence, Italy in January.)

It's clear that Durer took immense pains to capture every plane and shadow on Katharina's beautiful face, from the way her nostrils flare delicately, to the network of fine cross-hatchings with which he depicts her eyelids.

The girl's expression of a soft melancholy is rendered so exquisitely, that the viewer would give anything to make her smile.

"Durer spent his whole life trying to define ideal beauty," Spicer says. "Finally, he gave up. I like to think that this was one of the portraits that convinced him that there isn't just one ideal, but multiples."